The interaction of light with nanometer scale diameter single and multiple silver nanowires, coated externally with a dielectric material, is studied with the finite-difference time-domain method. As would be expected, the surface plasmon polariton resonance positions for the single nanowires shift to the red as the thickness of the coating is increased. In the case of multiple nanowires, however, we find that the effect of the coating is similar to bringing bare nanowires closer together, i.e., it leads to greater light intensities between the wires and more complex spectra. (C) 2003 Elsevier B.V. All rights reserved.